How to Determine the Last Subnet

Hi

Im Planing to take the exam soon i have one quick question

if we have an IP address e.g. 192.168.10.0/30 how do i know the last subnet

i know the range will be 4 so its going to be like this

192.168.10.0 --- 192.168.10.3
192.168.10.4 --- 192.168.10.7
192.168.10.8 --- 192.168.10.11

and so on but then its big waste of time in the exam..

is there a way we can determine the last subnet...

thanks

You could always count backwards ...

The block size for the subnet mask that you mentioned is 4. The broadcast address for the final subnet is 192.168.10.255 so it's IP address range is 192.168.10.252 - 192.168.10.255.

This technique works whatever the subnet mask, for instance a /28 mask has a block size of 16 so the final subnet's IP address range will be 192.168.10.240 - 192.168.10.255.